1. Field
The present invention relates generally to means for suspending mud flaps from vehicles, and particularly, to flexible hangers for suspending mud flaps from vehicles.
2. Description of the Problem and Related Art
Virtually all vehicles operated on public highways are required by state law to be equipped with means for intercepting mud, water spray, gravel, etc., thrown rearward by the vehicle's wheels, the purpose being to protect following vehicles from damage and from obscured vision which could cause accidents.
Trucks and trailers may satisfy this requirement by hanging mud flaps rearward of exposed wheels. Depending upon the size and number of wheels, the mud flaps may be as large as two feet wide and three feet long. They are generally constructed of a comparatively thick sheet of tough, resilient material for strength and are sufficiently heavy not to sail out rearward at high vehicle speeds. Many types of vehicles have no structure above the exposed wheels, so it is necessary to cantilever mud flap hangers outwardly from frame members inwardly of the wheels. Mud Flaps are typically made from plastic or rubber in the form of a 0.19-0.5 inch thick sheet, and are 24 inches wide by 24-36 inches in height. A majority of mud flaps have a straight top with four holes for installation. The other popular mud flap style has an angled, or chamfered, top corner with two holes on the horizontal top edge and two-to-three holes on the angled edge. The angled version offers more clearance for trailer components.
In normal highway use, cantilevered mud flap hangers are subject to continual up and down flexing at or near the vehicle attachment point, caused by the weight of the mud flap and the bouncing and pitching of the vehicle to which they are attached. When inner ends of the hangers are rigidly attached to the vehicle or where there are 90 degree bends near the attachment point, such constant flexing rapidly causes metal fatigue and work hardening, with resultant breaking of the hanger often in only a very few months of service. One solution to this problem was addressed by U.S. Pat. No. 2,970,849 to Betts, which discloses a steel, cantilevered hanger configured with a spring coil outward of the 90 degree bend designed to permit the hanger to flex somewhat. Such a hanger is made from spring grade steel, hardened to retain its shape, and later derivatives of this design have the spring portion oriented vertically to permit more flexing in the vertical plane. Yet, despite its hardness, the hanger in the field is often bent as a result of the hanger accidentally contacting some object, e.g, a trailer, a pole, etc. An alternative cause for bending comes from pinching the mud flap between the tire and an object on the ground when the vehicle backs up. The pinched mud flap rolls around the tire and pulls the hanger down with significant force.
Testing has shown that conventional steel cantilevered hangers, even those with a spring portion, will fail just from normal road vibration at a point near the 90 degree bend above the chassis mount. The result is very undesirable, not only because the lost hanger and mud flap must be replaced, but also because following vehicles may be hit by the falling hanger and mud flap or may cause an accident by swerving to miss a falling or fallen hanger and mud flap. Furthermore, producing such hangers is expensive because special materials and heat treatment are required and, if the heat treatment is improper, the spring may be too weak and allow the mud flap to sag into contact with the wheels or the pavement, or the spring may be too brittle and break. Finally, being made of steel, the conventional cantilevered hanger is heavy and susceptible to corrosion.
Accordingly, a mud flap hanger assembly is needed which is lightweight, inexpensive, and yet resilient enough to withstand vibration and the other myriad stresses from which conventional mud flap hangers currently fail.